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  <H1>SNMP support for Perl 5: Changes</H1>

  <p> Copyright (c) 1995-2009, Simon Leinen<br>
  All rights reserved </p>

  <em> This program is free software; you can redistribute it under
  the <a href="http://language.perl.com/misc/Artistic.html">"Artistic
  License"</a> included in this distribution. </em>

  <p>Author: <A HREF="http://www.switch.ch/misc/leinen/">Simon
Leinen</A> &lt;<A
HREF="mailto:simon.leinen@switch.ch">simon.leinen@switch.ch</A>&gt;</p>

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<h2> Recent Changes: </h2>

<ul>

<li> SNMP_Session.pm 1.14: <tt>open_trap_session</tt> now takes an
  optional <tt>ipv4only</tt> argument.  It defaults to 1, but by
  passing 0, you can create a session that accepts traps over IPv6 in
  addition to IPv4.  The <tt>receive_trap</tt> method has been
  enhanced by returning an additional value which is the address
  family.  There is a new <tt>receive_trap_1</tt> method, which
  differs from <tt>receive_trap</tt> in that it simply returns the
  trap and a sockaddr structure, rather than the trap, the host
  address, the port, and the address family. </li>

<li> BER.pm 1.14: Added POD documentation.  Started adding automated
  unit tests. </li>

<li> SNMP_Session.pm 1.14: Added POD documentation. </li>

<li> SNMP_util.pm 1.13: Parse OIDs in NOTIFICATION-TYPE names.  Change
 by Mike Mitchell/jaccobs. </li>

<li> SNMP_Session.pm 1.13: Fixed the optional socket-reuse code to
 handle IPv4 and IPv6 sockets separately. </li>

<li> SNMP_Session.pm 1.12: Upgraded to Artistic License 2.0 upon a
  suggestion from Tom Callaway. </li>

<li> SNMP_util.pm 1.12: Rewritten MIB parsing code from Mike
 Mitchell. </li>

<li> SNMP_util.pm 1.11: Improvement to loop detection in snmpwalk.
  Should cope with more broken agents.  Change by Mike Mitchell. </li>

<li> SNMP_Session.pm 1.10: Mike Fischer reported that on some systems,
 notably Linux, <tt>recv()</tt> may block even though a
 preceding <tt>select()</tt> for readability has returned
 successfully.  Once condition where this can happen is when a UDP
 checksum on an incoming datagram doesn't verify.  To avoid our
 library from blocking in this case, we have to
 pass <tt>MSG_DONTWAIT</tt> to <tt>recv()</tt>.  This behaviour is
 selected by a new optional argument to <tt>receive_response_3</tt>,
 and used by <tt>request_response_5</tt>. </li>

<li> SNMP_util.pm 1.09: Fix from Mike Mitchell for parsing qualified
 symbolic OIDs. </li>

<li> SNMP_Session.pm 1.08: Fixed a bug in the SNMPv2c version of
<tt>map_table_start_end</tt> that would cause errors when the
<samp>$end</samp> argument is actually being used.  Thanks to Jan van
Keulen for submitting the patch. </li>

<li> SNMP_Session.pm 1.07: Fixed <tt>strict&nbsp;subs</tt> error with
newer versions of Perl.  Thanks to Gerry Dalton for spotting
this. </li>

<li> SNMP_Session.pm 1.06: <tt>decode_trap_request</tt> now
understands SNMPv2 inform requests in addition to SNMPv1 traps and
SNMPv2 traps.  Contributed by Andrew Cornford-Matheson. </li>

<li> SNMP_util.pm 1.06: <tt>snmpwalkhash</tt> fix by Laurent
Girod. </li>

<li> <tt>index.html</tt>: The code is no longer available from
<tt>ftp.switch.ch</tt>, but via HTTP from
<tt>www.switch.ch</tt>. </li>

<li> SNMP_Session.pm 1.05: No change; version incremented for
<tt>SNMP_util.pm</tt> and <tt>BER.pm</tt>. </li>

<li> BER.pm 1.05: Internal restructuring: The new (BER.pm 1.02)
pretty-printer registration method is now used for most standard SNMP
types, too. </li>

<li> SNMP_util.pm 1.04: The subroutines <tt>snmpget</tt>,
<tt>snmpgetnext</tt> and <tt>snmpset</tt> will now detect when they
are called in scalar context, and return only the first (and typically
the only) of the retrieved values in this case. </li>

<li> SNMP_util.pm 1.03: Added a missing part of Mike Mitchell
pretty-printer registration patch. </li>

<li> BER.pm 1.02: Additional decoders (``pretty printers'') can now be
registered and unregistered for type codes using the
<tt>register_pretty_printer</tt> and
<tt>unregister_pretty_printer</tt> subroutines.  Implemented by Mike
Mitchell. </li>

<li> BER.pm 1.02: Corrected encoding of large integer-like
values. </li>

<li> SNMP_util.pm 1.02: <tt>snmpwalkhash</tt> now takes an additional
optional argument that should be a reference to a hash.  If used,
<tt>snmpwalkhash</tt> will insert the retrieved values into that
hash. </li>

<li> BER.pm 1.01: Properly parse the variant length format in
integers.  Thanks to <a href="mailto:milen@batmbg.com">Milen
Pavlov</a> for pointing out this bug.  Also, decoding should be
slightly more efficient in general, because one <tt>substr()</tt>
operation per (sub-) object has been eliminated. </li>

<li> SNMP_Session 1.00: Added Luc Pauwels' implementation of the
<tt>use_16bit_request_ids</tt> option.  Some SMC devices seem to
require this. </li>

<li> SNMP_Session 0.99: Improved request ID generation so that
<tt>avoid_negative_request_ids</tt> is always obeyed. </li>

<li> SNMP_util 0.99: Added <tt>Gauge32</tt> support to
<tt>snmpset</tt>.  Thanks to <a
href="mailto:tengi@CS.Princeton.EDU">Christopher J. Tengi</a> for the
idea.  Mike Mitchell provided new code that supports all known
types. </li>

<li> SNMP_Session 0.98: Portability fix in IPv6 support. </li>

<li> SNMP_util 0.98: Support encoding of OIDs containing multiple
quoted strings. </li>

<li> SNMP_util 0.97: Added support for TimeTicks values in
<tt>snmpset</tt>.  Patch from <a
href="mailto:JOERG.KUMMER@Roche.COM">Joerg Kummer</a> </li>

<li> SNMP_Session 0.97: Exported
<tt>$SNMP_Session::default_avoid_negative_request_ids</tt>, by
Philippe Simonet. </li>

<li> SNMP_Session 0.97: IPv6 support added by Valerio Bontempi and
Lorenzo Colitti. </li>

<li> SNMP_Session 0.96: Intermediate version with IPv6 support; not
published. </li>

<li> BER.pm 0.95: Fixed operator precedence bug in
decode_sequence(). </li>

<li> SNMP_Session.pm 0.94: A new slot <tt>capture_buffer</tt> has been
added to the SNMP_Session classes, courtesy <a
href="mailto:jakob.ilves@oracle.com">Jakob Ilves</a>.  See the sample
script <tt>test/capturetest.pl</tt> for an example of how to use
this. </li>

<li> BER.pm 0.94: New subroutines <tt>pretty_generic_sequence</tt>,
<tt>decode_generic_tlv</tt>, courtesy <a
href="mailto:jakob.ilves@oracle.com">Jakob Ilves</a>. </li>

<li> BER.pm 0.94: <tt>decode_by_template</tt>, <tt>decode_oid</tt>,
<tt>decode_sequence</tt>, <tt>decode_string</tt>: Explicitly signal
error when the PDU is undefined or too short.  This improves error
handling for some malformed PDUs, as generated by certain test
suites. </li>

<li> SNMP_Session.pm 0.93: There's a new variable
<tt>$default_avoid_negative_request_ids</tt>.  If it is set to a
non-zero value, newly created <tt>SNMP_Session</tt> objects will be
configured so that only request IDs in the range 0..2<sup>31</sup>-1
will be used.  This is needed to work around a bug in several SNMP
agents.  If you sometimes see requests fail, and the error message
always shows a negative request ID when that happens, please notify
the vendor of your agent of the bug.  While the vendor fixes the
problem, you can set the variable mentioned above to work around the
bug.  The problem has been described in a few mails on the
<em>mrtg-developers</em> mailing list that can hopefully be found <a
href="http://www.ee.ethz.ch/~slist/mrtg-developers/msg01609.html">here</a>
in the archive. </li>

<li> SNMP_util.pm 0.93: <tt>snmpwalk</tt> now will walk multiple OID
trees simultaneously.  If more than one OID is passed to the function,
the returned <em>OID:value</em> pairs will contain the entire OID
instead of just the leaf from the starting point. </li>

<li> SNMP_util.pm 0.93: <tt>snmpwalkhash</tt> now passes the textual
OID of the starting point as the seventh argument to the passed-in
hash function. </li>

<li> SNMP_util.pm 0.92: New subroutine <tt>snmpmaptable4</tt>, which
allows specifying the <em>max-repeaters</em>. </li>

<li> SNMP_util.pm 0.92: New MIB parsing code.  Most MIBs are processed
in one pass, but if an OID cannot be fully resolved, an extra pass is
done.  Also, <samp>OBJECT-GROUP</samp> entries are now
recognized. </li>

<li> SNMP_util.pm 0.92: The string-to-OID conversion routines now
transparently convert quoted strings to instance indexes.  For
example, <samp>"/usr"</samp> (including the quotes) would be converted
to <samp>4.47.118.97.114</samp>.

<li> SNMP_Session.pm 0.91: Fixed a bug in <tt>map_table_start_end</tt>
for <tt>SNMPv2_Session</tt> (which uses <tt>get-bulk</tt>) which had
caused a superfluous query after the entire table has already been
provably traversed.  Thanks to Michael Deegan for pointing this
out. </li>

<li> SNMP_util.pm 0.90: New version from Mike Mitchell.
 <tt>snmpwalkhash</tt> and <tt>snmpwalk</tt> now share most
 code. </li>

<li> SNMP_util.pm 0.90: Corrected handling of the optional port number in
 <tt>snmpopen</tt>. </li>

<li> test/if-counters.pl: Support 64-bit counters, and use
<tt>ifAlias</tt> to portably get interface descriptions. </li>

<li> SNMP_util.pm 0.89: New version from Mike Mitchell, with new
 <tt>snmpwalkhash</tt> subroutine by <a
 href="mailto:girod.laurent@pmintl.ch">Laurent Girod</a>. </li>

<li> SNMP_Session.pm 0.89: Made <tt>lenient_source_port_matching</tt>
the default. </li>

<li> SNMP_util.pm 0.89: Fixed a long-standing bug where the code would
generate PDUs with <tt>request-id</tt>s with large positive values,
violating the SNMP spec which mandates that <tt>request-id</tt>s be
<tt>Integer32</tt>s.  Thanks to Sergio Macedo <macedo@tmp.com.br> for
finding this bug. </li>

<li> SNMP_util.pm 0.88: Added missing <samp>use&nbsp;Carp;</samp>
statements in packages <samp>SNMPv1_Session</samp> and
<samp>SNMPv2_Session</samp>.  Thanks to <a
href="mailto:michael@cnspc18.murdoch.edu.au">Michael Deegan</a>. </li>

<li> SNMP_util.pm 0.87: No change from 0.86, but increased version
number to reflect change in BER.pm (SNMPv2 exception codes). </li>

<li> BER.pm 0.87: <samp>pretty_print</samp> now silently returns undef
when decoding SNMPv2 exception codes (<tt>noSuchObject</tt>,
<tt>noSuchInstance</tt>, or <tt>endOfMibView</tt>, see RFC 1905).
Original patch by <a href="mailto:driehuis@playbeing.org">Bert
Driehuis</a>. </li>

<li> BER.pm 0.86: <samp>pretty_print</samp> now silently returns undef
when given an undefined value, rather than issuing incomprehensible
warnings. </li>

<li> SNMP_util.pm 0.86: New <samp>snmpmaptable</samp> subroutine.
This is a more user-friendly version of <samp>map_table</samp> and is
described in the <a href="dist/README.SNMP_util">README.SNMP_util</a>
file.  From Mike Mitchell. </li>

<li> SNMP_util.pm 0.86: Support for the awesome <tt>get-bulk</tt>
operator, both directly through the new <samp>snmpgetbulk</samp>
subroutine, and transparently via <samp>snmpwalk</samp> when the
session's SNMP version is &gt;= 2 and the <samp>use_getbulk</samp>
slot is set (as it is by default).  From Mike Mitchell. </li>

<li> SNMP_Session.pm 0.85: If a local address is specified in
<samp>snmpopen</samp>, don't convert it using <samp>inet_aton</samp>,
because this is handled by the Socket library.  Fix from <a
href="mailto:mikem@open.com.au">Mike McCauley</a>. </li>

<li> SNMP_Session.pm 0.85: Added
<samp>lenient_source_port_matching</samp> slot to the session object.
Set this to communicate with weird SNMP agents that send the response
from a port other than 161.  Suggestion from <a
href="mailto:hgomez@slib.fr">Henri Gomez</a>. </li>

<li> SNMP_util.pm 0.84: New version from Mike Mitchell.
<samp>snmpopen</samp> now parses an optional hash argument for
options.  Also reintroduced defaulting of the UDP port to 161 for
``normal'' sessions. </li>

<li> SNMP_Session.pm 0.84: Clarified documentation concerning the
<samp>%pretty_oids</samp> hash, upon a suggestion from <a
href="mailto:alistair@alizta.com">Alistair Mills</a>. </li>

<li> SNMP_Session.pm 0.83: The source address in response packets is
now ignored when matching responses against outstanding queries.  In a
couple of previous revisions, the source address in response packets
had to match the destination address in the corresponding query.
Unfortunately some agents may use a different source address in
responses.  If you want the strict behavior back, you can send the
<tt>lenient_source_address_matching</tt> slot of the session object to
zero. </li>

<li> SNMP_Session.pm 0.83: The source address for outgoing packets can
now be specified as an additional optional argument to
<tt>open</tt>.  If you don't specify it, the system will choose the
source address by itself, usually corresponding to the interface on
which packets are sent. </li>

<li> SNMP_Session.pm 0.83: Fixed a bug which had caused requests to be
resent upon receipt of packets which don't match the outstanding
query. </li>

<li> SNMP_Session.pm 0.82: Fixed retry logic to avoid sending a last
retry without waiting for the response anymore.  Thanks to <a
href="mailto:wardenb@eluminant.com">Brett T Warden</a> for the
fix. </li>

<li> BER.pm 0.82: OIDs with only two subids can now be encoded.  The
most common case is the "null" OID (0.0).  Thanks to <a
href="mailto:wardenb@eluminant.com">Brett T Warden</a> for pointing out
that this didn't work. </li>

<li> BER.pm 0.82: pretty_print() now handles UInteger32 objects.
Patch by <a href="mailto:wardenb@eluminant.com">Brett T
Warden</a>. </li>

<li> BER.pm 0.81: Subids in the range 2^31 - 2^32-1 are now encoded
correctly.  Thanks to <a href="mailto:rik.hoorelbeke@pandora.be">Rik
Hoorelbeke</a> for noticing the problem. </li>

<li> SNMP_Session.pm 0.81: A cosmetic bug in the SNMPv2 version of
<tt>map_table</tt> (which uses <tt>get-bulk</tt>) was corrected.  The
user-supplied function is now always called on the same number of
arguments.  Before this, missing values at the end of a table row
would lead to the function being called with fewer arguments.  Now
there will be <tt>undef</tt> values for those, too.  Thanks to <a
href="mailto:schmid@switch.ch">Ulrich Schmid</a> for pointing this
out. </li>

<li> SNMP_Session.pm 0.80: A portability bug was fixed in the code
that matches incoming responses to outstanding requests.  The bug had
manifested itself, notably on some FreeBSD versions, by timeouts
waiting for responses, because the library thought the responses came
from another address than the corresponding requests had been sent
to. </li>

<li> SNMP_Session.pm 0.79: A new variable
<tt>$SNMP_Session::recycle_socket</tt> has been introduced.  When this
variable is set to a non-zero value (the default is zero), all newly
created SNMP_Session objects will share the same UDP socket.  This
saves file descriptors and system calls, but will cause problems with
multiple outstanding SNMP requests on different session objects.
Applications which don't perform parallel/asynchronous SNMP requests
can safely set this variable to reduce OS overhead somewhat.
Suggestion from <a href="mailto:schmid@switch.ch">Ulrich
Schmid</a>. </li>

<li> SNMP_Session.pm 0.79: The handling of incoming packets from
unexpected addresses has been cleaned up.  If a packet is received
from an IP address other than the one to which the request has been
sent, this packet is silently ignored, as mandated by the SNMP
standard. </li>

<li> SNMP_Session.pm 0.79: Receive-only session objects (such as the
ones created by <tt>open_trap_session</tt> now have <samp>undef</samp>
as the <samp>remote_addr</samp> value, rather than IP address
<samp>0.0.0.0</samp>. </li>

<li> BER.pm 0.79: There are new exported subroutines for encoding
different types of values: <samp>encode_uinteger32</samp>,
<samp>encode_counter32</samp>, <samp>encode_counter64</samp>,
<samp>encode_gauge32</samp>. </li>

<li> SNMP_Session.pm 0.78: The <tt>map_table</tt> implementation for
SNMPv2 sessions has been completely rewritten to reliably support
tables with holes in them.  Note that this hasn't been completely
validated or tested yet, but at least it has been found to handle
common cases reasonably. </li>

<li> BER.pm 0.77: Added support for long integers, so that
<tt>Counter64</tt> values can be handled without risk of losing
precision (due to automatic coercion to floating-point representation
by Perl).  When a BER-encoded integer is so long that it might not fit
in a 32-bit unsigned integer, then we use <tt>Math::BigInt</tt>
arithmetics to convert it. <b>Warning:</b> code which calls the
decoding functions should be prepared to handle <tt>Math::BigInt</tt>
values if <tt>Counter64</tt> values can be accessed.  In most respect,
those long integers behave just like ordinary integers.  A notable
exception is that they print with a leading ``<tt>+</tt>'' sign. </li>

<li> SNMP_Session 0.77: The SNMPv2 implementation of
<tt>map_table_start_end</tt> has been enhanced to cope with the case
where a response PDU ends with a truncated table row, courtesy <a
href="mailto:pee@gblx.net">Paul E. Erkkila</a>.  Note that tables with
missing entries still aren't handled correctly when SNMPv2 (and thus
the <tt>get-bulk</tt> operator is used). </li>

<li> SNMP_util 0.73: Added a fix from <a
href="mailto:mcm@unx.sas.com">Mike Mitchell</a> (originally <a
href="mailto:demel@zid.tuwien.ac.at">Johannes Demel</a>) to treat
<tt>OBJECT-IDENTITY</tt> like <tt>OBJECT IDENTIFIER</tt>.

<li> SNMP_Session 0.76: Added some debugging support for
<tt>map_table</tt>, which still doesn't work reliably when the SNMPv2
<tt>get-bulk</tt> operator is used. </li>

<li> test/if-counters.pl: Added <samp>-c</samp> option to enable
Cisco-specific variables (which are no longer retrieved by default as
in previous versions). </li>

<li> SNMP_Session 0.75: Fixed a bug in versions 0.73-0.74 where
creation of trap listener sockets would fail.  Rather than using
<tt>bind</tt> to bind to the trap port, we now pass a
<tt>LocalPort</tt> argument to <tt>INET-&gt;new</tt>. </li>

<li> SNMP_Session 0.75: Parse SNMPv2-Trap-Requests in addition to
SNMPv1 ones.  A caller can tell whether an SNMPv1 or an SNMPv2 request
has been received by testing whether the SNMPv1-specific fields are
defined.  The sample script <tt>test/trap-listener</tt> has been
updated to understand SNMPv2 Traps. </li>

<li> SNMP_Session 0.75: New subroutine <tt>v2_trap_request_send</tt>
which sends SNMPv2 Trap PDUs.  The sample script
<tt>test/trap-send</tt> has been extended to generate either type of
trap on request. </li>

<li> SNMP_Session 0.74: Put under copyright and Artistic
License. </li>

<li> SNMP_util 0.72: Changed <tt>snmpgetnext</tt> so it will return
the next lexicographical larger OID number, even if it is not in the
same OID tree.  Before the change snmpget would discard the return
value if the OID wasn't in the same tree.  In <tt>snmpMIB_to_OID</tt>,
an "unitialized variable" warning was removed. (Changes by <a
href="mailto:mcm@unx.sas.com">Mike Mitchell</a>, the author) </li>

<li> SNMP_Session 0.73: The UDP socket associated with each SNMP
session object is now created using <tt>IO::Socket::INET-&gt;new</tt>.
Before this change, a Perl file descriptor name was generated for each
new socket.  Apparently this caused a file descriptor leak.  The new
code is much cleaner and doesn't have that problem anymore.  Hopefully
the newly introduced dependency on the Socket::IO module is not a
problem.  Thanks to <a href="mailto:elble@icculus.nsg.nwu.edu">Andrew
W. Elble</a> for suggesting this change. </li>

<li> BER.pm 0.72: A new variable,
<tt>$BER::pretty_print_timeticks</tt>, has been introduced to give
users control over the degree of pretty-printing of <tt>TimeTicks</tt>
values.  If left at the defaults, <tt>TimeTicks</tt> values will be
converted to strings such as <samp>14&nbsp;days,&nbsp;6:56:07</samp>.  If you
set it to zero, the same value will simply pretty-print as
<samp>123456789</samp>, which should be interpreted in units (ticks)
of 10ms. </li>

<li> SNMP_util.pm 0.71: New subroutines <tt>snmpLoad_OID_Cache</tt> and
<tt>snmpQueue_MIB_File</tt> for loading MIBs in compact format. </li>

<li> SNMP_util.pm 0.71: <tt>snmpset</tt> now accepts <tt>ipaddr</tt>
as a type specifier. </li>

<li> SNMP_util.pm 0.70: <a href="mailto:mcm@unx.sas.com">Mike
Mitchell</a> added code for parsing MIB files.  See the description of
<tt>snmpMIB_to_OID</tt> in <a
href="dist/README.SNMP_util"><tt>README.SNMP_util</tt></a>. </li>

<li> SNMP_util.pm 0.69: Enable parsing of community strings which
contain <samp>@</samp> characters. </li>

<li> SNMP_util.pm 0.58: Check for errors from <tt>encode_oid</tt>, so
that illegal OIDs generate error messages.  Allow for suppression of
warnings by setting <tt>$SNMP_Session::suppress_warnings</tt> to a
value greater than one. </li>

<li> SNMP_Session.pm 0.68: Added methods <tt>receive_request</tt> and
<tt>decode_request</tt> to support SNMP agents.  Contributed by <a
href="mailto:mikem@open.com.au">Mike McCauley</a>. </li>

<li> SNMP_Session.pm 0.67: Implement a <tt>map_table_start_end</tt>
method for <tt>SNMPv2c_Session</tt> which uses <tt>get-bulk</tt>.  See
<a href="#map-table-4-use">Walking Tables With <tt>get-bulk</tt></a>
for more information. </li>

<li> SNMP_Session.pm 0.66: Fix from <a
href="mailto:Alan.Nichols@Ebay.Sun.COM">Alan Nichols</a> to the
handling of error replies.  In the last few revisions of SNMP_Session,
requests to which the agent responded with a non-zero
<tt>errorStatus</tt> were erroneously retried. </li>

<li> SNMP_Session.pm 0.66: When the <tt>errorStatus</tt> is zero, we
don't care about the <tt>errorIndex</tt>.  This makes us liberal
enough to cope with very old versions of the CMU agent code which
sometimes put a non-zero <tt>errorIndex</tt> in normal response
packets. </li>

<li> BER.pm 0.66: Changed the <tt>$VERSION</tt> number to be in line
with SNMP_Session.pm's. </li>

<li> BER.pm 0.66: Changed <tt>encode_oid</tt> so that it signals an
error when passed an illegal Object ID, such as one whose first subid
isn't 0, 1 or 2.  This should help people who try to use output from
CMU/UCD SNMP directly in MRTG. </li>

<li> SNMP_Session.pm 0.65: Fix error message when binding to UDP port
fails (<a href="mailto:jzhukovs@staff.juno.com">Jonathan
Zhukovsky</a>). </li>

<li> SNMP_util.pm 0.57: Small change to avoid warnings with "-w" when
session parameters are defaulted. </li>

<li> SNMP_util.pm 0.56: New subroutine <tt>snmpmapOID</tt>, <a
href="mailto:mcm@unx.sas.com">Mike Mitchell</a>. </li>

<li> SNMP_Session.pm 0.64: Fix of a bug in the detection of missing
responses by <a href="mailto:mcm@unx.sas.com">Mike Mitchell</a>. </li>

<li> SNMP_Session.pm 0.63: Fixed response matching logic to ignore
 out-of-sequence responses.  This has been a long-standing bug which
 made it very hard to use a single session object for multiple queries
 to devices that are (sometimes) slow in responding. </li>

<li> SNMP_Session.pm 0.62: Scoping problem with pretty_address()
 fixed. </li>

<li> Makefile.PL: New file which allows for easy installation
 according to standard Perl convention.  Kudos to <a
 href="mailto:clintdw@netcom.com">Clinton Wong</a>. </li>

<li> SNMP_Session.pm 0.61: The sender address of the last response
 received for a session is stored in
 <em>$session-&gt;{'last_sender_addr'}</em>.  In connection with
 broadcast or multicast addresses, this can be used to discover SNMP
 agents listening to specific communities, as illustrated in
 <tt>test/discover</tt>. </li>

<li> SNMP_Session.pm 0.60: Added support for <a
 href="#trap-recv">receiving SNMPv1 traps</a>. </li>

<li> SNMP_session.pm 0.59: Added methods <tt>set_timeout</tt>,
 <tt>set_retries</tt>, and <tt>set_backoff</tt> that can be used to
 tune the retransmission algorithm.  Fixed a bug in <tt>map_table</tt>
 that would cause an index of "0" to terminate the table walk. </li>

<li> SNMP_util.pm 0.54: First version to be distributed with the
 package, courtesy <a href="mailto:mcm@unx.sas.com">Mike
 Mitchell</a>. </li>

<li> BER.pm 0.58: Added <tt>encode_timeticks()</tt> subroutine.  This
 was used in the sample script for <a href="#trap-send">sending
 traps</a>, but was only defined in <tt>test/trap-test.pl</tt>.
 Thanks to <a href="mailto:bergerg@att.net">Gary Berger</a> for
 noticing this. </li>

<li> BER.pm 0.57: Added <tt>encode_ip_address()</tt> subroutine on a
 suggestion by <a href="mailto:mdiehn@mindspring.net">Mike
 Diehn</a>. </li>

<li> SNMP_Session 0.58: Added support for generating traps, courtesy
 <a href="mailto:mcm@unx.sas.com">Mike Mitchell</a>, see <a
 href="#trap-send">Sending Traps</a>. </li>

<li> <tt>test/ber-test.pl</tt>: Added more test cases contributed by
 <a href="mailto:mcm@unx.sas.com">Mike Mitchell</a>. </li>

<li> SNMP_Session 0.57: table walking support See ``<a
 href="#map-table-use">Walking Tables</a>'' below for how this is
 used. </li>

<li> BER 0.56: New <tt>encode_int()</tt> subroutine contributed by <a
href="mailto:mcm@unx.sas.com">Mike Mitchell</a>.  Fixes incorrect
encoding in the range +-2^15-2^23 and generalized to integers of any
size. </li>

<li> BER 0.55: Fix an arithmetic bug in the uptime
pretty-printer. Kudos to <a href="mailto:niels@euro.net">Niels
Bakker</a> for noticing this. </li>

<li> SNMP_Session 0.56: Fix a bug which occurs when an error should be
signaled while an SNMPv1_Session is being opened.  Noticed by <a
href="mailto:dcox@lexmark.com">Dan Cox</a> and <a
href="mailto:pakhomenko@gmd.de">Iouri Pakhomenko</a>. </li>

<li> BER 0.52: Ignore a leading dot when encoding an OID.  This is to
avoid trouble when people cut&amp;paste OIDs from CMU/UCD SNMP, where
a leading dot is used to mark a "fully qualified" OID. </li>

<li> SNMP_Session 0.55: The SNMP_Session module no longer calls
<tt>warn</tt> when the variable
<tt>$SNMP_Session::suppress_warnings</tt> is set to non-zero (it is
zero by default).  The error message from SNMP_Session can be
retrieved as <tt>$SNMP_Session::errmsg</tt>. </li>

<li> SNMP_Session 0.54, BER.pm 0.51: Errors in the BER module are now
passed upwards by the SNMP_Session module.  Before this change, one
could not distinguish malformed SNMP responses from no response at
all.  The BER module now no longer calls die(), but returns undefined
values. </li>

<li> Added <tt>test/arp</tt> which prints the NetToMedia table from a
remote host. </li>

<li> SNMP_Session 0.53: Avoid passing numeric IP addresses to
<tt>inet_ntoa()</tt>, by <a href="mailto:dan_needles@INS.COM">Daniel
L. Needles</a> </li>

<li> SNMP_Session 0.52: setRequest support based on code contributed
by <a href="mailto:matter@media.mit.edu">Matthew Trunnell</a>.  See
``<a href="#set-req-use">Set Requests</a>'' below for how this is
used. </li>

<li> SNMP_Session 0.51: Improved error messages by printing the
session in error messages if possible, and the OID and error message
whenever the agent sends back an error. </li>

<li> SNMP_Session 0.50, BER 0.50: The <b>BER</b> and
<b>SNMP_Session</b> modules both have version numbers according to the
convention in <b>Exporter.pm</b>.  That is, you can now insist on a
minimal version of the modules by saying e.g.

<pre>
use BER "0.50";
use SNMP_Session "0.52";
</pre>

 The initial version numbers are 0.50 for both modules. </li>

<li> The pretty printer should now print unsigned 32-bit values (such
 as Counters and Gauges) correctly, i.e. values larger than
 2<sup><font size="-2">31</font></sup> are printed as large positive
 numbers rather than negative numbers.  Note that this can cause
 problems depending on how you handle the output of the pretty
 printer, since those string representations of large numbers may not
 be convertible to integers using <b>atoi()</b> or similar
 functions. </li>

<li> The subroutines in SNMP_Session never call <b>die()</b> anymore
 if it encouters error situations.  Instead, they issue a warning and
 return <b>undef</b>.  <a href="mailto:btr@iol.unh.edu">Brad
 Ritchie</a> managed to convince me that library code should never
 <b>die</b>.  Unfortunately I haven't revised <b>BER.pm</b> yet, so
 subroutines related with BER transfer syntax encoding and decoding
 may still <b>die</b>. </li>

<li> The code has been cleaned up to use more of the standard
 functionality of the Perl 5 <b>Socket.pm</b> module.  That should
 have eliminated some potential portability problems (and delegated
 responsability for potential bugs :-).  Note that this means that the
 code requires Perl 5.002 or later. </li>

<li> Both source files now make extensive use of <b>strict</b> for
 better compile-time error checking.  Please notify me in case you
 have any problems because of this. </li>

<li> The library now attempts to retransmit queries for which no
 reponse has been received during a given time.  The default
 parameters for the retransmission logic have been discussed at length
 in the <em>mrtg</em> mailing list, and seem to work quite well, both
 against overloaded routers that simply drop some SNMP requests and
 against routers that are behind slow or lossy links.  If you have
 feedback on the default parameters, please drop me an e-mail. </li>

<li> When I implemented the retransmission logic, I also fixed
 handling of request IDs.  In older versions, the request ID was never
 changed between reqeuest, which could lead to (late) resposes being
 associated with the wrong request.  Now the request ID is incremented
 for each request, and mismatching responses are ignored.  For
 retransmissions, the request ID isn't changed.  If we did change it,
 we could estimate response time and implement an adaptive
 retransmission algorithm.  This has been left for further
 study. </li>

<li> Added code contributed by <em>mrtg</em> users:

 <ul>

  <li> Encoding of larger subids, by <a
 href="mailto:sip00@vg.swissptt.ch">Philippe Simonet</a> and <a
 href="mailto:yhu@casc.com">Yufang HU</a> </li>

  <li> Decoding <b>sysUpTime</b>, by <a
 href="mailto:dlr@Bungi.com">Dave Rand</a> </li>

  <li> Decoding longer (unsigned) integers, by <a
 href="mailto:tobi@oetiker.ch">Tobias Oetiker</a> </li>

  <li> Decoding longer strings, by <a
 href="mailto:san@iem.pw.edu.pl">Andrzej Tobola</a> </li>

  <li> More reasonable socket initialization, by <a
 href="mailto:peters@dkrz.de">Heine Peters</a> </li>

  <li> Correct integer BER-encoding, by <a
 href="mailto:mcm@unx.sas.com">Mike Mitchell</a> </li>

 </ul> </li>

</ul>


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